CN110024554B

CN110024554B - Control device

Info

Publication number: CN110024554B
Application number: CN201811532038.8A
Authority: CN
Inventors: 井本翼; 木曾田雄星; 山中之史; 西田圭佑; 西田智士; 川添翼; 加藤裕治; 仲岛铁弥; 高崎和也; 池田博; 中林隆志
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2018-01-10
Filing date: 2018-12-14
Publication date: 2022-09-23
Anticipated expiration: 2038-12-14
Also published as: JP6910970B2; KR20190085471A; JP2019120372A; KR102523878B1; CN110024554A

Abstract

The invention provides a control device for a work vehicle, which can stabilize the operation of the work vehicle when a servo mechanism is abnormal. The left HST (33) and the right HST (34) are configured to include a hydraulic pump (41) driven by the power of the engine (31) and a hydraulic motor (42) driven by pressure oil discharged from the hydraulic pump (41). Servomechanisms (66) for controlling the inclination angle of the swash plate of the hydraulic pump (41) are provided in correspondence with the left-side HST (33) and the right-side HST (34), respectively. If an abnormality such as a failure occurs in the servo mechanism (66), a fail-safe operation is executed. During the fail-safe operation, the output from both the left side HST (33) and the right side HST (34) corresponding to the left and right pair of running devices is stopped according to the detection of the abnormality of the servo mechanism (66) corresponding to one of the left and right pair of running devices, and the fail-safe operation is performed.

Description

Control device

Technical Field

The present invention relates to a control device for a work vehicle such as a combine harvester.

Background

Conventionally, a combine harvester equipped with a hydrostatic Transmission (HST) has been widely known. The hydrostatic continuously variable transmission includes a hydraulic pump and a hydraulic motor. In a combine equipped with a hydrostatic continuously variable transmission, a hydraulic pump is driven by power of an engine, a hydraulic motor is driven by oil discharged from the hydraulic pump, and power of the hydraulic motor is transmitted to left and right crawler belts.

The hydraulic circuit including the hydraulic pump and the hydraulic motor has, for example, a closed circuit structure, and the hydraulic pump is provided with a servo piston for changing the angle of a swash plate. By changing the swash plate angle of the hydraulic pump, the discharge direction and flow rate of oil from the hydraulic pump change, and the rotation direction and rotation speed of the hydraulic motor change. The drive method of the servo piston includes a mechanical type in which a shift lever provided on an operation panel of a driver's cab is mechanically connected to the servo piston and the servo piston is operated by operating the shift lever, and an electronic control type (electronic servo type) in which a current supplied to a pressure control valve composed of two proportional pressure reducing control valves is controlled and the servo piston is moved by a hydraulic pressure supplied from the pressure control valve to the servo piston.

Patent document 1: japanese patent laid-open No. 2009 and 30693

In a hydrostatic continuously variable transmission employing an electronic control system, if a servo mechanism including a servo piston and a pressure control valve fails, the swash plate angle of a hydraulic pump cannot be controlled, and further, the power transmitted from a hydraulic motor to a crawler belt cannot be controlled, so that the operation of the combine harvester is unstable.

Disclosure of Invention

The present invention aims to provide a control device for a work vehicle, which can stabilize the operation of the work vehicle when a servo mechanism is abnormal.

In order to achieve the above object, a control device for a work vehicle according to the present invention comprises: a control device for a work vehicle having mounted thereon: an engine; a pair of left and right traveling devices; a power transmission device including a continuously variable transmission including a pump driven by power of an engine and a motor driven by pressure oil discharged from the pump, and a servo mechanism controlling an angle of a pump swash plate of the pump, the power transmission device transmitting power of the motor to a pair of left and right traveling devices; the control device includes: an abnormality detection means for detecting an abnormality in the servo means; and a fail-safe mechanism for executing a fail-safe operation for stabilizing the operation of the work vehicle based on the detection of the abnormality by the abnormality detection mechanism.

According to this configuration, the power transmission device is mounted between the engine and the pair of left and right traveling devices. The power transmission device includes a continuously variable transmission including a pump driven by power of an engine and a motor driven by pressure oil discharged from the pump, and a servo mechanism for controlling a swash plate angle of the pump. The discharge direction and flow rate of oil from the pump are controlled by controlling the angle of the swash plate of the pump, and the rotation direction and rotation speed of the motor are controlled.

When an abnormality such as a failure occurs in the servo mechanism and the abnormality is detected, a fail-safe operation for stabilizing the operation of the work vehicle is executed. Therefore, the operation of the work vehicle can be stabilized when the servo mechanism is abnormal.

The continuously variable transmission and the servo mechanism may be provided corresponding to each of the pair of left and right traveling devices. In this case, the fail-safe mechanism may control the servo mechanisms corresponding to the left and right traveling devices, respectively, based on the detection of the abnormality of the servo mechanism corresponding to one of the left and right traveling devices by the abnormality detection mechanism, and may stop the output from both the continuously variable transmissions corresponding to the left and right traveling devices, respectively, as the fail-safe operation. This makes it possible to stop the machine body of the work vehicle, and to stabilize the operation of the work vehicle by stopping the machine body.

The configuration may be such that: the drive device includes an axle to which power is transmitted from the power transmission device, the continuously variable transmission and the servo mechanism are provided corresponding to each of the pair of left and right drive devices, and the power transmission device includes a clutch that engages to match the rotational speeds of the axles provided in each of the pair of left and right drive devices. In this case, the fail-safe mechanism may engage the clutch upon detection of an abnormality of the servo mechanism corresponding to one of the pair of left and right traveling devices by the abnormality detection mechanism, and may continue an output from the continuously variable transmission corresponding to the other of the pair of left and right traveling devices by controlling the servo mechanism corresponding to the other of the pair of left and right traveling devices, as a fail-safe operation. This makes it possible to drive the motor of the continuously variable transmission corresponding to the servo mechanism that operates normally, and to run the machine body while stabilizing the operation of the work vehicle by the power from the motor.

It may be constituted as follows: the servo mechanism includes a servo piston interlocked with a pump swash plate, an advance control valve for supplying hydraulic pressure for positioning the servo piston in a predetermined advance range to the servo piston, and a retreat control valve for supplying hydraulic pressure for positioning the servo piston in a predetermined retreat range to the servo piston, wherein the pump swash plate is at an angle at which pressurized oil in the advance direction is discharged from the pump when the servo piston is positioned in the advance range, and at an angle at which pressurized oil in the retreat direction is discharged from the pump when the servo piston is positioned in the retreat range, the pump outputs power in the advance direction of the work vehicle by supplying the pressurized oil in the advance direction, and outputs power in the retreat direction of the work vehicle by supplying the pressurized oil in the retreat direction. In this configuration, when the abnormality of the forward control valve is detected by the abnormality detection means, the fail-safe means may permit control of the reverse control valve as the fail-safe operation, and when the abnormality of the reverse control valve is detected by the abnormality detection means, the fail-safe means may permit control of the forward control valve as the fail-safe operation. Thus, the body can be made to travel forward by the control of the normally operating forward control valve, and can be made to travel backward by the control of the normally operating backward control valve. Therefore, the machine body can be caused to travel while stabilizing the operation of the work vehicle.

The work vehicle may further carry an operating member provided to be operable between a forward position on one side with respect to the neutral position and a reverse position on the other side with respect to the neutral position. In this case, the control device may further include: a position detection mechanism that detects a position of the operation member; a swash plate angle detection mechanism that detects an angle of a pump swash plate; a control mechanism for controlling the servo mechanism so that the angle of the pump swash plate is matched with a target angle corresponding to the position of the operating member detected by the position detection mechanism; the abnormality detection means detects an abnormality in the servo mechanism when a state in which a deviation between the target angle and the angle detected by the swash plate angle detection means is a predetermined value or more is maintained for a predetermined time.

The fail-safe operation when an abnormality of the servo mechanism is detected may be an operation to stop the engine. The engine can be stopped to stop the machine body, and the operation of the work vehicle can be stabilized by stopping the machine body.

The fail-safe operation may be an operation of idling the engine, or an operation of stopping the engine after the engine is idling in accordance with the position of the operating member detected by the position detecting means matching the neutral position. By idling the engine, the traveling speed of the machine body can be suppressed, and therefore, the travel of the machine body can be ensured while stabilizing the operation of the work vehicle.

In the case where the power transmission device is further provided with a control valve for switching the angle of the motor swash plate of the motor between a first angle at which the motor rotates at a relatively low speed and a second angle at which the motor rotates at a relatively high speed, the control valve may be controlled to set the swash plate of the motor at the first angle as a fail-safe operation. This can further suppress the traveling speed of the machine body, and can further stabilize the operation of the work vehicle.

The following may also be used: the engine control device further includes a storage means for storing the detection of the abnormality when the abnormality of the servo mechanism is detected by the abnormality detection means, and the fail-safe means prohibits the engine from being started while the abnormality of the servo mechanism is detected by the storage means. If the engine is started in a state where the abnormality has not been eliminated, the work vehicle may exhibit unstable operation, and by prohibiting the engine from being started, unstable operation of the work vehicle can be suppressed.

Effects of the invention

According to the present invention, the operation of the work vehicle in the event of an abnormality in the servo mechanism can be stabilized.

Drawings

Fig. 1 is a right side view showing a front portion of the combine harvester.

Fig. 2 is a diagram showing a structure of a part of a drive transmission system of the combine harvester.

Fig. 3 is a cross-sectional view showing the remaining part of the drive transmission system, and shows the drive transmission system from the hydraulic motors of the left HST and the right HST to the traveling device.

Fig. 4 is a block diagram showing a main part of an electrical configuration of a combine harvester according to an embodiment of the present invention.

Fig. 5 is a flowchart showing the flow of the fail-safe control.

Fig. 6 is a flowchart showing a flow of fail-safe control according to another embodiment.

Fig. 7 is a flowchart showing a flow of fail-safe control according to another embodiment.

Description of the reference numerals

1: combine harvester (working vehicle)

12: traveling device

21: main gear shift lever (operation parts)

31: engine

32: drive transmission system (Power transmission device)

41: hydraulic pump (Pump)

42: hydraulic motor (Motor)

58: servo piston

61: advancing pressure control valve (advancing control valve)

63: back pressure control valve (Back control valve)

66: servo mechanism

76: low speed switching valve (control valve)

77: high speed switching valve (control valve)

131: central clutch (Clutch)

142: ECU (control device, abnormality detection mechanism, fail-safe mechanism, control mechanism, storage mechanism)

153: main gear lever sensor (position detection mechanism)

159: pump swash plate position sensor (swash plate angle detection mechanism)

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

< combine harvester >

Fig. 1 is a right side view showing a front part of a combine harvester 1 according to an embodiment of the present invention.

The combine harvester 1 is a working vehicle that cuts and threshes grain and straw while traveling in a field. The body 11 of the combine harvester 1 is supported by a pair of left and right traveling devices 12. The travel device 12 employs a crawler belt having a capability of traversing uneven ground in order to enable the combine harvester 1 to travel in a field.

The machine body 11 is provided with a driving platform 13, a harvesting device 14, a threshing device 15 and a grain box 16.

The cab 13 is disposed above the front end of the traveling device 12. The cab 13 is provided with an operator seat 17 on which an operator sits, and operation panels 18 operated by the operator are provided, for example, in front of and on the left of the operator seat 17. The operation panel 18 includes a main shift lever 21, a steering lever 22, and the like.

The main shift lever 21 is provided to be able to deflect in the front-rear direction. The main shift lever 21 is biased to switch between forward and reverse of the body 11, and the forward and reverse speeds can be changed.

The steering rod 22 is provided to be capable of deflecting in the left-right direction and the front-rear direction. By the tilting operation of the steering lever 22 in the left-right direction, the straight running, the left turn, and the right turn of the machine body 11 can be switched. Further, the cutting device 14 can be lifted and lowered by the tilting operation of the steering lever 22 in the front-rear direction.

The harvesting device 14 is disposed in front of the traveling device 12. The harvesting device 14 includes a dividing straw 23 at a front end thereof, and a cutter 24 at a rear side of the dividing straw 23. The straw-separating rod 23 and the cutter 24 are supported by the harvesting device frame 25F. A harvesting cross frame 25L extending in the left-right direction is provided at the rear end of the harvesting device frame 25F. One end of the main cutting frame 25M is connected to the transverse cutting frame 25L. The main cutting frame 25M extends rearward from the transverse cutting frame 25L, and the other end (front-lower-rear-upper end, rear end) thereof is rotatably connected to the frame of the machine body 11. By the tilting operation of the steering rod 22 in the front-rear direction, a cylinder (not shown) is operated to swing the main cutting frame 25M, and by the swing, the main cutting frame can be raised and lowered between a raised position where the straw separating rod 23 and the cutting blade 24 are raised from the ground surface to a high position and a lowered position where the straw separating rod 23 and the cutting blade 24 are lowered to a position close to the ground surface. When the machine body 11 is moved forward with the branch straw 23 and the cutter 24 positioned at the lowered position, the straw is cut by the cutter 24 while the stem roots of the straw planted in the field are separated by the branch straw 23.

The threshing device 15 and the grain box 16 are arranged in parallel in the left-right direction above the traveling device 12 and at a position behind the harvesting device 14. The harvested straws are transported to the threshing device 15 by the harvesting device 14. The threshing device 15 transports the stem root side of the grain straw rearward by the threshing feeding chain, and supplies the ear tip side of the grain straw to the threshing chamber to thresh the grain straw. Then, the grains are transported from the threshing device 15 to the grain box 16, and the grains are stored in the grain box 16. A grain discharging auger 26 is connected to the grain tank 16, and grains stored in the grain tank 16 can be discharged to the outside of the machine body through the grain discharging auger 26.

< stepless speed change device >

Fig. 2 is a diagram showing a structure of a part of the drive transmission system 32 of the combine harvester 1. In fig. 2, the power transmission system from the engine 31 to the drive transmission system 32 is shown in a schematic view, and the structures related to the left HST33 and the right HST34 of the drive transmission system 32 are shown in a hydraulic circuit diagram.

The combine harvester 1 is equipped with an engine 31 and a drive transmission system 32 for transmitting power of the engine 31 to the traveling device 12.

The drive Transmission system 32 includes a left-side HST (Hydro Static Transmission) 33 and a right-side HST 34.

The left HST33 has a closed circuit structure in which the hydraulic pump 41 and the hydraulic motor 42 are connected by the first oil passage 43 and the second oil passage 44 to circulate the hydraulic oil between the hydraulic pump 41 and the hydraulic motor 42. The first oil passage 43 is connected to a first port 45 of the hydraulic pump 41 and a first port 46 of the hydraulic motor 42. The second oil passage 44 is connected to a second port 47 of the hydraulic pump 41 and a second port 48 of the hydraulic motor 42.

The left HST33 is provided with a supply pump 51. The feed pump 51 is a fixed displacement hydraulic pump, and discharges hydraulic oil to the feed oil passage 53 by rotation of the pump rotation shaft 52. The supply oil passage 53 is connected to the first oil passage 43 via a first check valve 54, and is connected to the second oil passage 44 via a second check valve 55. The supply oil passage 53 is connected to an oil tank 57 via an unloading valve 56.

The hydraulic pressure of the supply oil passage 53 is maintained at a predetermined supply pressure by the function of the unloading valve 56. When the hydraulic pressure of the first oil passage 43 is lower than the supply pressure, which is the hydraulic pressure of the supply oil passage 53, the first check valve 54 opens, and the hydraulic oil is supplied from the supply oil passage 53 to the first oil passage 43 via the first check valve 54. When the hydraulic pressure of the second oil passage 44 is lower than the supply pressure, the second check valve 55 opens, and the hydraulic oil is supplied from the supply oil passage 53 to the second oil passage 44 via the second check valve 55. Thereby, the hydraulic pressures of the first oil passage 43 and the second oil passage 44 are maintained at the supply pressure or higher.

The left HST33 is an integrated HST in which the hydraulic pump 41, the hydraulic motor 42, the first oil passage 43, the second oil passage 44, the first check valve 54, the second check valve 55, the unloading valve 56, and the like are housed in a single housing.

The hydraulic pump 41 is a variable displacement swash plate type piston pump, and includes a cylinder block, a plurality of pistons radially arranged in the cylinder block, a pump swash plate on which the pistons slide, and the like. The hydraulic pump 41 and the feed pump 51 have a pump rotating shaft 52 in common, and the cylinder is provided to rotate integrally with the pump rotating shaft 52.

In order to change the inclination angle of the swash plate of the hydraulic pump 41, an electronically controlled servo piston 58 is provided. The servo piston 58 has a first pressure chamber 62 and a second pressure chamber 64, the first pressure chamber 62 being supplied with hydraulic pressure from the forward pressure control valve 61, and the second pressure chamber 64 being supplied with hydraulic pressure from the reverse pressure control valve 63. The servo piston 58 has a rod 65 that moves linearly by a differential pressure between the first pressure chamber 62 and the second pressure chamber 64, and the tilt angle of the swash plate of the pump is changed by the linear movement of the rod 65. The servo piston 58, the forward pressure control valve 61, and the backward pressure control valve 63 constitute a servo mechanism 66 that controls the inclination angle of the swash plate of the hydraulic pump 41.

The discharge amount of the hydraulic oil from the hydraulic pump 41 decreases as the inclination angle of the pump swash plate of the hydraulic pump 41 with respect to the axis of the pump rotary shaft 52 (the rotation axis of the cylinder block) increases, and when the inclination angle of the pump swash plate is 90 °, the discharge of the hydraulic oil from the hydraulic pump 41 is stopped. When the inclination angle of the pump swash plate exceeds 90 ° (when the inclination is reversed), the discharge direction of the hydraulic oil from the hydraulic pump 41 is reversed as compared with when the inclination angle is smaller than 90 °.

The hydraulic motor 42 is a variable displacement swash plate type piston motor, and includes a motor rotary shaft 71, a cylinder block 72 (see fig. 3) that rotates integrally with the motor rotary shaft 71, a plurality of pistons 73 (see fig. 3) disposed radially in the cylinder block 72, a motor swash plate 74 (see fig. 3) that the pistons 73 press, and the like. When the inclination angle of the motor swash plate 74 of the hydraulic motor 42 with respect to the axis of the motor rotary shaft 71 (the rotation axis of the cylinder block) is constant, the rotation speed of the motor rotary shaft 71 increases as the amount of hydraulic oil supplied to the hydraulic motor 42, that is, the amount of hydraulic oil discharged from the hydraulic pump 41 increases.

In addition, when the amount of hydraulic oil supplied to the hydraulic motor 42 is constant, the rotation speed of the motor rotary shaft 71 decreases as the inclination angle of the motor swash plate 74 increases. To change the inclination angle of the motor swash plate 74 of the hydraulic motor 42, a sub-shifting piston 75 is provided. The sub-transmission piston 75 is connected to a low-speed switching valve 76 and a high-speed switching valve 77. By opening the low-speed switching valve 76 and closing the high-speed switching valve 77, hydraulic pressure is supplied from the low-speed switching valve 76 to the sub-transmission piston 75, so that the rod 78 of the sub-transmission piston 75 is positioned at the low-speed position, and the inclination angle of the motor swash plate 74 is relatively increased. On the other hand, by closing the low-speed switching valve 76 and opening the high-speed switching valve 77, hydraulic pressure is supplied from the high-speed switching valve 77 to the sub-transmission piston 75, so that the rod 78 of the sub-transmission piston 75 is positioned at the high-speed position, and the inclination angle of the motor swash plate 74 is relatively decreased. Therefore, the position of the motor swash plate 74 can be switched between a high-speed side position where the rotation speed of the motor rotary shaft 71 is relatively increased and a low-speed side position where the rotation speed of the motor rotary shaft 71 is relatively decreased by switching the opening/closing of the low-speed switching valve 76 and the high-speed switching valve 77.

Since the right HST34 has the same structure as the left HST33, the parts of the right HST34 corresponding to the parts of the left HST33 are denoted by the same reference numerals as the parts of the left HST33, and the description thereof is omitted.

The power of the engine 31 is input to each pump rotation shaft 52 of the left HST33 and the right HST 34. Specifically, a pulley 82 is provided on the output shaft 81 of the engine 31 so as not to rotate relative thereto. The drive transmission system 32 includes an input shaft 83 extending parallel to the output shaft 81 of the engine 31. A pulley 84 is provided on the input shaft 83 so as not to be relatively rotatable. An endless belt 85 is wound around the

pulleys

82 and 84. Further, an input gear 86 is provided on the input shaft 83 so as not to be relatively rotatable. The input gear 86 meshes with the intermediate gear 87, and the intermediate gear 87 meshes with the pump gear 88 provided in the pump rotating shaft 52 of the right HST34 so as not to be relatively rotatable. The pump gear 88 is engaged with a pump gear 89 provided in the pump rotating shaft 52 of the left HST33 so as not to rotate relatively.

Thereby, the power of the engine 31 is transmitted from the output shaft 81 to the pulley 84 via the pulley 82 and the belt 85, and the input shaft 83 rotates integrally with the pulley 84. The power (rotation) of the input shaft 83 is transmitted from the input gear 86 to the pump gear 88 of the right HST34 via the intermediate gear 87, and the pump rotation shaft 52 of the right HST34 is rotated in a predetermined direction integrally with the pump gear 88. The power of the input shaft 83 is transmitted from the input gear 86 to the pump gear 88 of the right HST34 via the intermediate gear 87, and then transmitted from the pump gear 88 to the pump gear 89, so that the pump rotation shaft 52 of the left HST33 and the pump gear 89 rotate together in the reverse direction of the predetermined direction. Therefore, when the inclination angles of the pump swash plates of the hydraulic pumps 41 of the left HST33 and the right HST34 are the same, the motor rotation shaft 71 of the hydraulic motor 42 of the left HST33 and the motor rotation shaft 71 of the hydraulic motor 42 of the right HST34 rotate in opposite directions to each other.

Fig. 3 is a cross-sectional view showing a part of the drive transmission system 32, and shows the structure from the hydraulic motor 42 of the left HST33 and the right HST34 to the traveling device 12.

The hydraulic motors 42 of the left HST33 and the right HST34 are arranged symmetrically with respect to each other such that the motor rotation shafts 71 (having a common axis) are aligned on the same axis and the axes thereof are parallel to the left and

right axles

91L, 91R.

Note that, in the following description, the motor rotation shaft 71 of the left HST33 is referred to as "motor rotation shaft 71L", and the motor rotation shaft 71 of the right HST34 is referred to as "motor rotation shaft 71R".

The

motor rotary shafts

71L, 71R are rotatably supported at their outer ends in the left-right direction by a unit case 101 forming the outer shell of the drive transmission system 32 via

bearings

102L, 102R, respectively. Motor output gears 103L and 103R are supported at inner ends of the

motor rotary shafts

71L and 71R in the left-right direction so as not to be relatively rotatable.

First, second, and third

intermediate shafts

104, 105, and 106 are provided between the

motor rotary shafts

71L and 71R and the

axles

91L and 91R at intervals so as to be parallel to the

axles

91L and 91R. The first intermediate shaft 104 is supported by the unit case 101 so as not to be rotatable. The left and right end portions of the second intermediate shaft 105 are rotatably supported by the unit case 101 via

bearings

107L and 107R, respectively. The left and right end portions of the third intermediate shaft 106 are rotatably supported by the unit case 101 via

bearings

108L and 108R, respectively.

The motor output gears 103L and 103R are respectively meshed with first

intermediate gears

111L and 111R rotatably held on the first intermediate shaft 104.

A second intermediate gear 112L and a third intermediate gear 113L are supported on the left side portion of the second intermediate shaft 105 so as not to be rotatable relative to each other. On the other hand, a third intermediate gear 113R is relatively rotatably supported via a needle bearing in a right portion of the second intermediate shaft 105. An annular second intermediate gear 112R is provided outside the third intermediate gear 113R so as to surround the third intermediate gear 113R. The inner peripheral portion of the second intermediate gear 112R is fixed to the third intermediate gear 113R. Thereby, the second intermediate gear 112R rotates integrally with the third intermediate gear 113R. The second intermediate gears 112L, 112R are engaged with the first

intermediate gears

111L, 111R, respectively. The third

intermediate gears

113L, 113R mesh with the fourth

intermediate gears

114L, 114R, respectively.

Fifth

intermediate gears

115L and 115R are supported by the third intermediate shaft 106 so as not to be rotatable relative to each other. The fourth

intermediate gears

114L and 114R are annular, and the fourth

intermediate gears

114L and 114R are provided so as to surround the outer sides of the fifth

intermediate gears

115L and 115R, respectively. Inner peripheral portions of the fourth

intermediate gears

114L, 114R are fixed to fifth

intermediate gears

115L, 115R, respectively. Thereby, the fourth

intermediate gears

114L, 114R rotate integrally with the fifth

intermediate gears

115L, 115R, respectively. The fifth

intermediate gears

115L, 115R mesh with the sixth

intermediate gears

116L, 116R.

A through hole 117 extending on the central axis is formed in the sixth intermediate gear 116L. The right end of the axle 91L is inserted into the through hole 117 from the left side, and the right end thereof is spline-coupled to the through hole 117. A cylindrical portion 118 having an outer diameter smaller than the inner diameter of the through hole 117 of the sixth intermediate gear 116L is formed at the left end portion of the sixth intermediate gear 116R. The columnar portion 118 is inserted into the through hole 117 from the right side, and is relatively rotatably held by the sixth intermediate gear 116L via a needle bearing. A circular recess 119 that is recessed to the left is formed at the right end of the sixth intermediate gear 116R. The left end of the axle 91R is inserted into the recess 119, and the left end thereof is spline-coupled to the recess 119.

Bearings

121L and 121R are fitted to the left end portion of the sixth intermediate gear 116L and the right end portion of the sixth intermediate gear 116R, respectively, and the outer rings of the

bearings

121L and 121R are fixedly held by the unit case 101, whereby the sixth

intermediate gears

116L and 116R are rotatably held by the unit case 101. The left end portion of the axle 91L and the right end portion of the axle 91R are rotatably held in the unit case 101 via

bearings

122L and 122R, respectively, and the

axles

91L and 91R are rotatably held in the unit case 101.

The left end portion of the axle 91L and the right end portion of the axle 91R are coupled to the

drive wheels

123L and 123R of the traveling device 12, respectively, so as not to be relatively rotatable.

The drive transmission system 32 includes a center clutch 131. The center clutch 131 is engaged and disengaged to connect and disconnect the second intermediate shaft 105 and the third intermediate gear 113R. That is, the second intermediate shaft 105 and the third intermediate gear 113R are coupled by engagement of the center clutch 131, and the second intermediate shaft 105 and the third intermediate gear 113R rotate integrally. By the release of the center clutch 131, the second intermediate shaft 105 is separated from the third intermediate gear 113, and the third intermediate gear 113 is rotatable with respect to the second intermediate shaft 105. The center clutch 131 is engaged and disengaged by hydraulic pressure.

The drive transmission system 32 is provided with a parking brake 132. The parking brake 132 is engaged and disengaged to brake and release the second intermediate shaft 105. That is, the second intermediate shaft 105 is braked so as not to rotate relative to the unit case 101 by the engagement of the parking brake 132. By disengaging the parking brake 132, the braking of the second intermediate shaft 105 is released, and the second intermediate shaft 105 is allowed to rotate relative to the unit case 101. The parking brake 132 is engaged and disengaged by manually operating a parking brake lever.

< Electrical Structure >

Fig. 4 is a block diagram showing a main part of an electrical structure of the combine harvester 1.

A single main ECU (Electronic Control Unit) 141 for overall unified Control and a plurality of ECUs 142 for individual specific Control are mounted on the combine harvester 1. One of the plurality of ECUs 142 is shown in fig. 4. The ECU142 shown in fig. 4 may be further subdivided by functions, and thus be constituted by a plurality of ECUs 142. Both the

ECUs

141 and 142 have a structure including a Micro Controller Unit (MCU).

The main ECU141 is communicably connected with each ECU142 for individual specific control. The main ECU141 receives information acquired by the respective ECUs 142 from detection signals of various sensors and the like, and transmits instructions and information necessary for control of the respective ECUs 142 to the respective ECUs 142. An instrument panel 151 disposed on the operation panel 18 (see fig. 1) of the driver's cab 13 is connected to the main ECU141 as a control target, and the main ECU141 controls various gauges such as a distance meter installed on the instrument panel 151 and a display 152. The display 152 is constituted by a liquid crystal display, for example.

A main shift lever sensor 153, a steering lever sensor 154, a left vehicle speed sensor 155, and a right vehicle speed sensor 156 are connected to an ECU142 (hereinafter simply referred to as "ECU 142") shown in fig. 4, the main shift lever sensor 153 outputs a detection signal corresponding to the operation position of the main shift lever 21, the steering lever sensor 154 outputs a detection signal corresponding to the operation position of the steering lever 22, the left vehicle speed sensor 155 outputs a pulse signal synchronized with the rotation of the left axle 91L as a detection signal, the right vehicle speed sensor 156 outputs a pulse signal synchronized with the rotation of the right axle 91R as a detection signal, and the ECU142 receives the detection signals of the main shift lever sensor 153, the steering lever sensor 154, the left vehicle speed sensor 155, and the right vehicle speed sensor 156.

Further, a forward valve current sensor 157, a reverse valve current sensor 158, and a swash plate position sensor 159 are connected to the ECU142, the forward valve current sensor 157 outputs a detection signal corresponding to a current value supplied to the forward pressure control valve 61 included in each of the left HST33 and the right HST34, the reverse valve current sensor 158 outputs a detection signal corresponding to a current value supplied to the reverse pressure control valve 63 included in each of the left HST33 and the right HST34, and the swash plate position sensor 159 outputs a detection signal corresponding to a position (angle) of a swash plate of the hydraulic pump 41 included in each of the left HST33 and the right HST34, and the ECU142 receives the detection signals of the forward valve current sensor 157, the reverse valve current sensor 158, and the swash plate position sensor 159.

In the combine harvester 1, a slow turning mode, a braking turning mode, and a pivot turning mode are set as modes of turning control (turning control modes) of the machine body 11. A turning mode switch 161 for switching the turning control mode is provided on the operation panel 18 of the cab 13. The turning mode switch 161 is a dial switch, and a gentle turning position, a brake turning position, and a pivot turning position corresponding to the turning control mode are set in the movable region thereof. The turn mode switch 161 has a knob that is held by a finger of an operator and is rotated, and outputs different signals depending on which position the knob is located among the slack turn position, the brake turn position, and the original turn position.

The ECU142 controls the operation of the forward pressure control valve 61, the reverse pressure control valve 63, the low speed switching valve 76, and the high speed switching valve 77 included in the engine 31, the left HST33, and the right HST34, and the operation of the center clutch 131, based on information obtained from detection signals of various sensors such as the main shift lever sensor 153, the steering lever sensor 154, the left vehicle speed sensor 155, the right vehicle speed sensor 156, the forward valve current sensor 157, the reverse valve current sensor 158, and the turning mode switch 161, and information input from the main ECU141 and the other ECU142, and controls the traveling and turning of the machine body 11.

< Driving control >

The travel of the machine body 11 is controlled by the ECU 142. In this travel control, the position of the main shift lever 21 is obtained from the detection signal of the main shift lever sensor 153.

When the position of the main shift lever 21 is the stop position, the respective opening degrees of the forward pressure control valve 61 and the reverse pressure control valve 63 are adjusted by controlling the currents supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 for each of the left HST33 and the right HST34, so that the inclination angle of the pump swash plate of the hydraulic pump 41 is set to 90 °. Accordingly, since the hydraulic oil is not discharged from the hydraulic pump 41, the hydraulic motor 42 does not rotate, and the power of the hydraulic motor 42 is not transmitted to the

axles

91L and 91R. Therefore, the traveling device 12 does not operate, and the machine body 11 stops.

When the main shift lever 21 is deflected forward from the stop position, the hydraulic pressure supplied from the forward pressure control valve 61 to the first pressure chamber 62 of the servo piston 58 is made greater than the hydraulic pressure supplied from the reverse pressure control valve 63 to the second pressure chamber 64 by controlling the currents supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 for each of the left HST33 and the right HST 34. As a result, a differential pressure is generated between the first pressure chamber 62 and the second pressure chamber 64, and the inclination angle of the pump swash plate of the hydraulic pump 41 is made smaller than 90 ° by the differential pressure. As a result, the hydraulic oil is discharged from the hydraulic pump 41, and the hydraulic motor 42 rotates by receiving the hydraulic oil. The rotation (power) of hydraulic motor 42 is transmitted to

axles

91L and 91R to rotate

drive wheels

123L and 123R of traveling device 12 in the forward direction integrally with

axles

91L and 91R, respectively, thereby moving body 11 forward.

When the main shift lever 21 is deflected rearward from the stop position, the hydraulic pressure supplied from the reverse pressure control valve 63 to the second pressure chamber 64 is made greater than the hydraulic pressure supplied from the forward pressure control valve 61 to the first pressure chamber 62 of the servo piston 58 by controlling the currents supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 for each of the left-side HST33 and the right-side HST 34. Thereby, a differential pressure is generated between the first pressure chamber 62 and the second pressure chamber 64, and the inclination angle of the pump swash plate of the hydraulic pump 41 is made larger than 90 ° by the differential pressure. As a result, the hydraulic oil is discharged from the hydraulic pump 41 in the direction opposite to the forward movement, and the hydraulic motor 42 receives the hydraulic oil and rotates in the direction opposite to the forward movement. The rotation (power) of the hydraulic motor 42 is transmitted to the

axles

91L and 91R, and the

drive wheels

123L and 123R of the traveling device 12 rotate in the backward direction integrally with the

axles

91L and 91R, respectively, to thereby retract the machine body 11.

The center clutch 131 is engaged when the machine body 11 moves forward and backward. The engagement of the center clutch 131 couples the second intermediate shaft 105 and the third intermediate gear 113R, and the second intermediate shaft 105 and the third intermediate gear 113R rotate integrally, so that the fourth

intermediate gears

114L and 114R rotate at the same speed. Therefore, the fifth

intermediate gears

115L, 115R rotate at the same speed, the sixth

intermediate gears

116L, 116R rotate at the same speed, and the

axles

91L, 91R rotate at the same speed. As a result, the left and

right drive wheels

123L, 123R of the traveling device 12 rotate at the same speed, and therefore the machine body 11 moves forward or backward with excellent straight running stability.

When the inclination angle of the pump swash plate of the hydraulic pump 41 is changed by controlling the current supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 during forward movement or reverse movement, the discharge amount of the hydraulic oil from the hydraulic pump 41 changes, and the rotation speed of the hydraulic motor 42 changes. Therefore, by adjusting the inclination angle of the pump swash plate of the hydraulic pump 41 in accordance with the amount of inclination of the main shift lever 21 from the stop position, the forward and backward speeds of the machine body 11 can be changed steplessly.

In the drive transmission system 32, as described above, the rotation speed of the hydraulic motor 42 can be switched between two stages, i.e., a relatively large high-speed stage and a relatively small low-speed stage, by switching the opening/closing of the low-speed switching valve 76 and the high-speed switching valve 77. Therefore, the forward and reverse speeds of the machine body 11 can be changed by switching between the high gear and the low gear. Note that a sub-shift lever (not shown) may be provided on the operation panel 18 of the driver's seat 13, and switching between the high-speed range and the low-speed range may be instructed by operating the sub-shift lever.

< turning control >

When the steering lever 22 is tilted from the center straight position to the left or right turning position during straight (forward/reverse) traveling of the machine body 11, the ECU142 starts turning control for turning the machine body 11.

In the turning control, it is determined from the output signal of the turning mode switch 161 whether the position of the turning mode switch 161 is a gentle turning position, a braking turning position, or an original turning position.

When the position of the turning mode switch 161 is the gentle turning position, the turning control mode is set to the gentle turning mode. In the normal turning control in the gentle turning mode, for example, a target value of the turning ratio, which is the target turning ratio, is set to 0.3. Then, the rotation speed of the traveling device 12 (one of the

drive wheels

123L, 123R) on the turning inner side is reduced by controlling the current (the inclination angle of the pump swash plate of the hydraulic pump 41) supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 of each of the left HST33 and the right HST34 so that the actual turning ratio (actual turning ratio) matches the target turning ratio.

The turning ratio is a speed ratio between the running gear 12 on the turning inner side and the running gear 12 on the turning outer side, specifically, when the turning outer side is on the left side, the turning ratio is a ratio between the rotation speed of the axle 91R on the right side, which is the turning inner side, and the rotation speed of the axle 91L on the left side, which is the turning outer side, and when the turning outer side is on the right side, the turning ratio is a ratio between the rotation speed of the axle 91L on the left side, which is the turning inner side, and the rotation speed of the axle 91R on the right side. The rotation speed of the left axle 91L can be calculated from the detection signal of the left vehicle speed sensor 155, and the rotation speed of the right axle 91R can be calculated from the detection signal of the right vehicle speed sensor 156. When the turning outer side is the left side, the actual turning ratio can be calculated by obtaining the ratio of the rotation speed of the axle 91R calculated from the detection signal of the right vehicle speed sensor 156 to the rotation speed of the axle 91L calculated from the detection signal of the left vehicle speed sensor 155. When the turning outer side is the right side, the actual turning ratio can be calculated by obtaining the ratio of the rotation speed of the axle 91L calculated from the detection signal of the left vehicle speed sensor 155 and the rotation speed of the axle 91R calculated from the detection signal of the right vehicle speed sensor 156.

When the position of the turning mode switch 161 is the braking turning position, the turning control mode is set to the braking turning mode. In the normal turning control in the brake turning mode, for example, the target turning ratio is set to 0. Then, the current supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 of each of the left HST33 and the right HST34 is controlled so that the actual turning ratio matches the target turning ratio, thereby decreasing the rotation speed of the running gear 12 on the turning inner side. When the target turning ratio is 0, the target speed of the running gear 12 on the turning inner side is 0. Therefore, in the normal turning control when the position of the turning mode switch 161 is the braking turning position, the currents supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 of the left HST33 and the right HST34 are controlled so as to stop the traveling device 12 on the turning inner side.

In the case where the position of the turning mode switch 161 is the pivot turning position, the turning control mode is set to the pivot turning mode. In the normal turning control in the pivot turning mode, the target value of the turning ratio (target turning ratio) is obtained by inverting the rotational direction of the running gear 12 on the turning inner side and giving a negative sign (-) to the value of the rotational speed of the running gear 12 on the turning inner side, and the target value of the turning ratio (target turning ratio) is set to-0.3. Then, the currents supplied to the forward pressure control valve 61 and the reverse pressure control valve 63 of the left HST33 and the right HST34 are controlled so that the actual turning ratio matches the target turning ratio.

< failsafe action >

Fig. 5 is a flowchart showing the flow of fail-safe control.

In order to operate the combine harvester 1 to the safe side (fail-safe operation) when an abnormality such as a failure that the travel control cannot be normally performed occurs, the fail-safe control is executed by the ECU 142.

In the fail-safe control, it is determined whether or not an abnormality affecting the running control is occurring in the servo 66 corresponding to the left HST33 and the right HST34 from the detection signals of the forward valve current sensor 157 and the reverse valve current sensor 158 (step S11).

Note that, hereinafter, the servo piston 58 corresponding to the left HST33 is referred to as "left servo 66", and the servo piston 58 corresponding to the right HST34 is referred to as "right servo 66".

As an example of the abnormality of the servo mechanism 66, when a fault that the signal lines of the forward valve current sensor 157 and the reverse valve current sensor 158 are disconnected is cited, the disconnection fault includes a disconnection fault of the forward valve current sensor 157 of the left servo mechanism 66, a disconnection fault of the reverse valve current sensor 158 of the left servo mechanism 66, a disconnection fault of the forward valve current sensor 157 of the right servo mechanism 66, and a disconnection fault of the reverse valve current sensor 158 of the right servo mechanism 66.

If there is no abnormality in at least one of the left or right servomechanisms 66 (no in step S11), the fail-safe control is not further performed.

When an abnormality occurs in at least one of the left or right servos 66 (yes in step S11), the drive of the left HST33 and the right HST34 is stopped in response to the occurrence of the abnormality (step S12). The body 11 is stopped by stopping the driving of the left HST33 and the right HST 34.

After that, it is determined whether or not an instruction to enter the emergency mode from the normal mode is input (step S13). The normal mode is a mode in which normal travel control is executed, and the emergency mode is a mode in which the machine body 11 can be temporarily caused to travel when an abnormality occurs. An instruction to enter the emergency mode is input to the ECU142 by operating an operation unit (for example, a touch panel disposed on the display 152 in a superposed manner) provided in an instrument panel 151 of the driver's cab 13 or a switch provided in the operation panel 18. Before the instruction to enter the emergency mode is input, the left HST33 and the right HST34 are kept stopped, and the machine body 11 cannot travel.

When the instruction to enter the emergency mode is input (yes in step S13), it is determined whether or not the generated abnormality is only a forward abnormality that disables the normal forward travel of the machine body 11 (step S14). For example, when only the open failure of the forward valve current sensor 157 occurs, it is determined that only the forward abnormality has occurred.

If only the forward error has occurred (yes at step S14), it is determined whether or not a forward command has been input (step S15). Specifically, it is determined whether the main shift lever 21 is deflected to the front side from the detection signal of the main shift lever sensor 153.

When the main shift lever 21 is deflected to the front side (yes in step S15), the center clutch 131 is engaged (step S16).

Then, the left or right servo 66, which can be normally operated among the left or right servos 66, is controlled, and the hydraulic motor 42 of the left HST33 or the right HST34 corresponding to the servo 66 is driven in the forward direction (step S17). For example, when the open-circuit failure occurs in only the forward valve current sensor 157 of the left servo mechanism 66, the hydraulic motor 42 of the right HST34 is driven in the forward direction. Since the center clutch 131 is engaged, the left and

right drive wheels

123L, 123R of the running device 12 rotate in the forward direction at the same speed by the power output from the hydraulic motor 42 of the left HST33 or the right HST 34. As a result, the body 11 advances.

If the forward command is not input (no in step S15), it is determined whether a reverse command is input (step S18). Specifically, it is determined whether the main shift lever 21 is deflected to the rear side from the detection signal of the main shift lever sensor 153.

When the main shift lever 21 is deflected to the rear side when the forward abnormality occurs (yes in step S18), the machine body 11 can normally travel backward, and therefore the hydraulic motors 42 of the left HST33 and the right HST34 are driven in the backward direction by the same control as the travel control in the normal mode (step S19). Thereby, the body 11 retreats.

When either the forward command or the reverse command is not input, that is, when the main shift lever 21 is not operated to be tilted from the stop position (no in step S18), it is determined whether or not the main switch provided on the operation panel 18 is operated to the "off" position for stopping the engine 31, that is, whether or not the engine stop operation is performed (step S20).

When the engine stop operation is performed (yes in step S20), the engine 31 is stopped, and the fail-safe control is ended. If the engine stopping operation is not performed (no in step S20), it is determined again whether a forward abnormality is occurring (step S14).

If the forward abnormality has not occurred (no in step S14), it is determined whether or not the abnormality occurred is only a reverse abnormality that prevents the machine body 11 from traveling normally in reverse (step S21). For example, when only the disconnection failure of the reverse valve current sensor 158 occurs, it is determined that only the reverse abnormality has occurred.

If only the reverse abnormality has occurred (yes at step S21), it is determined whether a reverse command has been input (step S22). Specifically, it is determined whether the main shift lever 21 is deflected to the rear side from the detection signal of the main shift lever sensor 153.

When the main shift lever 21 is deflected to the rear side (yes in step S22), the center clutch 131 is engaged (step S23).

Then, the left or right servo 66, which can normally operate among the left or right servos 66, is controlled, and the hydraulic motor 42 of the left HST33 or the right HST34 corresponding to the servo 66 is driven in the backward direction (step S24). For example, when the open-circuit failure occurs in only the reverse valve current sensor 158 of the right servo mechanism 66, the hydraulic motor 42 of the left HST33 is driven in the forward direction. Since the center clutch 131 is engaged, the left and

right drive wheels

123L, 123R of the running device 12 are rotated in the forward direction at the same speed by the power output from the hydraulic motor 42 of the left HST33 or the right HST 34. As a result, the body 11 advances.

If the reverse command is not input (no in step S22), it is determined whether or not a forward command is input (step S25). Specifically, it is determined whether the main shift lever 21 is deflected to the front side from the detection signal of the main shift lever sensor 153.

When the main shift lever 21 is deflected toward the front side when the reverse abnormality occurs (yes in step S25), the machine body 11 can normally travel forward, and therefore the hydraulic motors 42 of the left HST33 and the right HST34 are driven in the forward direction by the same control as the travel control in the normal mode (step S26). Thereby, the body 11 advances.

When either the forward command or the reverse command is not input, that is, when the main shift lever 21 is not operated to be tilted from the stop position (no in step S25), it is determined whether or not the engine stop operation is performed (step S20).

When the engine stop operation is performed (yes in step S20), the engine 31 is stopped, and the fail-safe control is ended. If the engine stop operation is not performed (no in step S20), it is determined again whether a forward abnormality is occurring (step S14).

Note that, in the case where both the forward abnormality and the reverse abnormality occur (no in step S21), the fail-safe control ends.

< action Effect >

According to this configuration, the drive transmission system 32 is installed between the engine 31 and the pair of left and right traveling devices 12. In the drive transmission system 32, a left HST33 and a right HST34 are provided corresponding to the pair of left and right traveling devices 12, respectively. Both the left HST33 and the right HST34 include a hydraulic pump 41 driven by the power of the engine 31 and a hydraulic motor 42 driven by pressure oil discharged from the hydraulic pump 41. Further, in the drive transmission system 32, servos 66 for controlling the inclination angle of the pump swash plate of the hydraulic pump 41 are provided corresponding to the left HST33 and the right HST34, respectively. The discharge direction and flow rate of the oil from the hydraulic pump 41 are controlled by controlling the inclination angles of the pump swash plates of the left HST33 and the right HST34, and the rotation direction and rotation speed of the hydraulic motor 42 are controlled.

When an abnormality such as a failure occurs in the servo mechanism 66 and the abnormality is detected, a fail-safe operation for stabilizing the operation of the combine harvester 1 is executed. In the fail-safe operation, when an abnormality of the servo 66 corresponding to one of the pair of left and right running devices 12 is detected, first, as the fail-safe operation, the output from both the left HST33 and the right HST34 corresponding to the pair of left and right running devices 12 is stopped. This makes it possible to stop the machine body 11 of the combine harvester 1, and by stopping the machine body 11, the operation of the combine harvester 1 can be stabilized.

The running device 12 includes

axles

91L and 91R to which power is transmitted from the drive transmission system 32. The drive transmission system 32 includes a center clutch 131 that engages to match the rotation speeds of the

axles

91L and 91R. In the fail-safe operation, after the output of the left HST33 and the right HST34 is stopped, the center clutch 131 is engaged to control the normally operating servo 66 so as to continue the output from the left HST33 or the right HST34 corresponding to the normally operating servo 66. Accordingly, the hydraulic motor 42 of the left HST33 or the right HST34 corresponding to the servo mechanism 66 that operates normally can be driven, and the machine body 11 can be driven while stabilizing the operation of the combine harvester 1 by the power from the hydraulic motor 42.

< other embodiments >

During the traveling control, a target swash plate angle, which is a control target value of the inclination angle of the pump swash plate of the hydraulic pump 41, is set based on the position of the main shift lever 21 obtained from the detection signal of the main shift lever sensor 153. Further, an actual inclination angle (actual swash plate angle) of the pump swash plate of the hydraulic pump 41 is acquired from a detection signal of the pump swash plate position sensor 159. Then, the forward pressure control valve 61 and the reverse pressure control valve 63 included in the servo mechanism 66 are controlled so that the deviation between the target swash plate angle and the actual swash plate angle approaches 0.

In the fail-safe control shown in fig. 6, the ECU142 refers to the target swash plate angle set in the travel control (step S31). In addition, the actual swash plate angle acquired in the running control is referred to (step S32).

Then, it is determined whether or not a state in which the deviation between the target swash plate angle and the actual swash plate angle is equal to or greater than a certain value is maintained for a certain time (step S33).

When the deviation between the target swash plate angle and the actual swash plate angle is smaller than a predetermined value, or when the deviation between the target swash plate angle and the actual swash plate angle is equal to or larger than the predetermined value but the time during which the deviation is equal to or larger than the predetermined value continues is smaller than a predetermined time ("no" in step S33), the target swash plate angle and the actual swash plate angle are referred to again (steps S31 and S32). Then, it is determined again whether or not the state where the deviation is equal to or more than a certain value is maintained for a certain time (step S33).

If the state in which the deviation between the target swash plate angle and the actual swash plate angle is equal to or greater than a predetermined value is maintained for a predetermined time (yes in step S33), it is determined that an abnormality such as a failure of the forward pressure control valve 61 and the reverse pressure control valve 63 or a failure in which the signal lines of the forward valve current sensor 157 and the reverse valve current sensor 158 are disconnected occurs in the servo mechanism 66. In this case, the engine 31 is stopped (step S34).

< action Effect >

In this way, when an abnormality such as a failure occurs in the servo 66 and the abnormality is detected, the engine 31 is stopped. By stopping the engine 31, the hydraulic pump 41 is stopped from driving, and thus the machine body 11 of the combine harvester 1 can be stopped. By stopping the machine body 11, the operation of the combine harvester 1 can be stabilized.

< third embodiment >

Fig. 7 is a flowchart showing a flow of fail-safe control according to the third embodiment.

In the fail-safe control shown in fig. 7, the ECU142 refers to the target swash plate angle set in the travel control (step S41). In addition, the actual swash plate angle acquired in the running control is referred to (step S42).

Then, it is determined whether or not a state in which the deviation between the target swash plate angle and the actual swash plate angle is equal to or greater than a certain value is maintained for a certain time (step S43).

When the deviation between the target swash plate angle and the actual swash plate angle is smaller than a predetermined value, or when the deviation between the target swash plate angle and the actual swash plate angle is equal to or larger than the predetermined value but the time during which the deviation is equal to or larger than the predetermined value continues is smaller than a predetermined time ("no" in step S43), the target swash plate angle and the actual swash plate angle are referred to again (steps S41 and S42). Then, it is determined again whether or not the state where the deviation is equal to or more than a certain value is maintained for a certain time (step S43).

If the state in which the deviation between the target swash plate angle and the actual swash plate angle is equal to or greater than the predetermined value is maintained for a predetermined time (yes in step S43), it is determined that an abnormality has occurred in the servo mechanism 66. In this case, the low-speed switching valve 76 provided corresponding to the hydraulic motor 42 is opened, and the high-speed switching valve 77 is closed so that the motor swash plate 74 of the hydraulic motor 42 is positioned on the low-speed side (step S44). Further, the engine 31 is set to an idling state (step S45).

After that, when the main shift lever 21 is returned to the stop position (yes in step S46), the engine 31 is stopped (step S47).

In addition, a state in which an abnormality (error) has occurred in the servo mechanism 66 (for example, the magnitude of the deviation between the target swash plate angle and the actual swash plate angle, etc.) is stored in the nonvolatile memory in the ECU142 (step S48).

Subsequently, the start of the engine 31 is prohibited (step S49), and the fail-safe control is ended.

< action Effect >

When an abnormality such as a failure occurs in the servo mechanism 66 and the abnormality is detected, the motor swash plate 74 of the hydraulic motor 42 is set to the low speed side, and the engine 31 is set to the idling state. This enables the machine body 11 to travel at a low speed. The travel of the machine body 11 can be ensured while stabilizing the operation of the combine harvester 1, and the combine harvester 1 can be moved to a safe position.

After that, when the main shift lever 21 is returned to the stop position (neutral position), the engine 31 is stopped. Further, the error state is stored in the nonvolatile memory, and thereafter, the engine 31 is prohibited from starting until the error state is eliminated. This can suppress unstable operation of the combine harvester 1.

< modification example >

Although the embodiments of the present invention have been described above, the present invention can be implemented in other embodiments, and various design changes can be made to the above configuration within the scope of the matters described in the claims.

Claims

1. A control device, for a work vehicle,

the work vehicle is provided with: an engine; a pair of left and right traveling devices; a power transmission device including a continuously variable transmission including a pump driven by power of the engine and a motor driven by pressure oil discharged from the pump, and a servo mechanism controlling an angle of a pump swash plate of the pump, the power transmission device transmitting the power of the motor to the pair of left and right traveling devices;

the control device includes:

an abnormality detection means for detecting an abnormality of the servo means;

a fail-safe mechanism that executes a fail-safe operation for stabilizing an operation of the work vehicle based on detection of the abnormality by the abnormality detection mechanism;

the traveling device includes an axle to which power is transmitted from the power transmission device,

the continuously variable transmission and the servo mechanism are provided corresponding to the pair of left and right traveling devices,

the power transmission device includes a clutch engaged to match the rotation speeds of the axles of the pair of left and right traveling devices,

the fail-safe operation is performed by the fail-safe mechanism engaging the clutch and controlling the servo mechanism corresponding to the other of the pair of left and right running devices to continue the output from the continuously variable transmission corresponding to the other of the pair of left and right running devices, in response to detection of an abnormality of the servo mechanism corresponding to one of the pair of left and right running devices by the abnormality detection mechanism.

2. The control device of claim 1,

the fail-safe mechanism controls the servo mechanisms corresponding to the left and right running devices, respectively, based on the detection of the abnormality of the servo mechanism corresponding to one of the left and right running devices by the abnormality detection mechanism, to stop the output from both the continuously variable transmissions corresponding to the left and right running devices, respectively, as the fail-safe operation.

3. The control device of claim 1,

the servo mechanism includes a servo piston interlocked with the pump swash plate, an advance control valve for supplying hydraulic pressure for positioning the servo piston in a predetermined advance range to the servo piston, and a retreat control valve for supplying hydraulic pressure for positioning the servo piston in a predetermined retreat range to the servo piston, wherein the pump swash plate is at an angle at which pressurized oil in an advance direction is discharged from the pump when the servo piston is positioned in the advance range, and at an angle at which pressurized oil in a retreat direction is discharged from the pump when the servo piston is positioned in the retreat range,

the pump outputs power in a forward direction of the work vehicle by supplying the pressurized oil in the forward direction, and outputs power in a backward direction of the work vehicle by supplying the pressurized oil in the backward direction,

the fail-safe mechanism allows control of the reverse control valve as the fail-safe operation when the abnormality of the forward control valve is detected by the abnormality detection mechanism, and allows control of the forward control valve as the fail-safe operation when the abnormality of the reverse control valve is detected by the abnormality detection mechanism.

4. The control device of claim 1,

the work vehicle further includes an operating member provided to be operable between a forward position on one side with respect to a neutral position and a reverse position on the other side with respect to the neutral position,

the control device further includes:

a position detection mechanism that detects a position of the operation member;

a swash plate angle detection mechanism that detects an angle of the pump swash plate;

a control unit that controls the servo unit so that an angle of the pump swash plate matches a target angle corresponding to the position of the operating member detected by the position detection unit;

the abnormality detection means detects an abnormality of the servo mechanism when a state in which a deviation between the target angle and the angle detected by the swash plate angle detection means is a predetermined value or more is maintained for a predetermined time.

5. The control apparatus according to claim 4,

the fail-safe mechanism stops the engine as the fail-safe operation.

6. The control device of claim 4,

the fail-safe mechanism sets the engine to an idling state as the fail-safe operation.

7. The control device of claim 6,

the fail-safe mechanism makes the engine in an idling state correspond to the position of the operating member detected by the position detecting mechanism and the neutral position, and makes the engine start

The machine is stopped as the fail-safe action.

8. The control device according to any one of claims 4, 6, and 7,

the power transmission device further includes a control valve that switches an angle of a motor swash plate of the motor between a first angle at which the motor rotates at a relatively low speed and a second angle at which the motor rotates at a relatively high speed,

the fail-safe mechanism controls the control valve such that the swash plate of the motor is at the first angle, as the fail-safe operation.

9. The control device according to any one of claims 4 to 7,

the control device further includes a storage means for storing a detection of an abnormality in the servo means when the abnormality detection means detects an abnormality in the servo means,

the fail-safe mechanism prohibits the engine from being started while the storage mechanism stores therein the detection of the abnormality of the servo mechanism.